# Serial Interface

The **serial** input plugin, allows to retrieve messages/data from a *Serial* interface.

## Configuration Parameters

| Key        | Description                                                                                                                                              |
| ---------- | -------------------------------------------------------------------------------------------------------------------------------------------------------- |
| File       | Absolute path to the device entry, e.g: /dev/ttyS0                                                                                                       |
| Bitrate    | The bitrate for the communication, e.g: 9600, 38400, 115200, etc                                                                                         |
| Min\_Bytes | The serial interface will expect at least *Min\_Bytes* to be available before to process the message (default: 1)                                        |
| Separator  | Allows to specify a *separator* string that's used to determinate when a message ends.                                                                   |
| Format     | Specify the format of the incoming data stream. The only option available is 'json'. Note that *Format* and *Separator* cannot be used at the same time. |

## Getting Started

In order to retrieve messages over the *Serial* interface, you can run the plugin from the command line or through the configuration file:

### Command Line

The following example loads the input *serial* plugin where it set a Bitrate of 9600, listen from the */dev/tnt0* interface and use the custom tag *data* to route the message.

```
$ fluent-bit -i serial -t data -p File=/dev/tnt0 -p BitRate=9600 -o stdout -m '*'
```

The above interface (/dev/tnt0) is an emulation of the serial interface (more details at bottom), for demonstrative purposes we will write some message to the other end of the interface, in this case */dev/tnt1*, e.g:

```
$ echo 'this is some message' > /dev/tnt1
```

In Fluent Bit you should see an output like this:

```bash
$ fluent-bit -i serial -t data -p File=/dev/tnt0 -p BitRate=9600 -o stdout -m '*'
Fluent Bit v1.x.x
* Copyright (C) 2019-2020 The Fluent Bit Authors
* Copyright (C) 2015-2018 Treasure Data
* Fluent Bit is a CNCF sub-project under the umbrella of Fluentd
* https://fluentbit.io

[2016/05/20 15:44:39] [ info] starting engine
[0] data: [1463780680, {"msg"=>"this is some message"}]
```

Now using the *Separator* configuration, we could send multiple messages at once (run this command after starting Fluent Bit):

```
$ echo 'aaXbbXccXddXee' > /dev/tnt1
```

```
$ fluent-bit -i serial -t data -p File=/dev/tnt0 -p BitRate=9600 -p Separator=X -o stdout -m '*'
Fluent-Bit v0.8.0
Copyright (C) Treasure Data

[2016/05/20 16:04:51] [ info] starting engine
[0] data: [1463781902, {"msg"=>"aa"}]
[1] data: [1463781902, {"msg"=>"bb"}]
[2] data: [1463781902, {"msg"=>"cc"}]
[3] data: [1463781902, {"msg"=>"dd"}]
```

### Configuration File

In your main configuration file append the following *Input* & *Output* sections:

```python
[INPUT]
    Name      serial
    Tag       data
    File      /dev/tnt0
    BitRate   9600
    Separator X

[OUTPUT]
    Name   stdout
    Match  *
```

## Emulating Serial Interface on Linux

The following content is some extra information that will allow you to emulate a serial interface on your Linux system, so you can test this *Serial* input plugin locally in case you don't have such interface in your computer. The following procedure has been tested on Ubuntu 15.04 running a Linux Kernel 4.0.

## Build and install the tty0tty module

Download the sources

```bash
$ git clone https://github.com/freemed/tty0tty
```

Unpack and compile

```bash
$ cd tty0tty/module
$ make
```

Copy the new kernel module into the kernel modules directory

```bash
$ sudo cp tty0tty.ko /lib/modules/$(uname -r)/kernel/drivers/misc/
```

Load the module

```bash
$ sudo depmod
$ sudo modprobe tty0tty
```

You should see new serial ports in /dev/ (ls /dev/tnt\*) Give appropriate permissions to the new serial ports:

```bash
$ sudo chmod 666 /dev/tnt*
```

When the module is loaded, it will interconnect the following virtual interfaces:

```bash
/dev/tnt0 <=> /dev/tnt1
/dev/tnt2 <=> /dev/tnt3
/dev/tnt4 <=> /dev/tnt5
/dev/tnt6 <=> /dev/tnt7
```